8000 Initial UQuantity and tests. · astropy/astropy@ef14802 · GitHub
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Initial UQuantity and tests.
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‎astropy/uncertainty/__init__.py

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# Licensed under a 3-clause BSD style license - see LICENSE.rst
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from __future__ import absolute_import
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from core import *
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from .core import *
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from .uquantity import *

‎astropy/uncertainty/core.py

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# -*- coding: utf-8 -*-
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# Licensed under a 3-clause BSD style license - see LICENSE.rst
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from __future__ import (absolute_import, division, print_function,
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np.sin: np.cos,
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np.sinh: np.cosh,
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np.sqrt: lambda x: 0.5/np.sqrt(x),
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np.square: lambda x: 2.0*x,
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np.tan: lambda x: 1+np.tan(x)**2,
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np.tanh: lambda x: 1-np.tanh(x)**2}
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UFUNC_DERIVATIVES[np.divide] = UFUNC_DERIVATIVES[np.true_divide]
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UFUNC_DERIVATIVES[np.abs] = UFUNC_DERIVATIVES[np.fabs]
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if hasattr(np, 'cbrt'):
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UFUNC_DERIVATIVES[np.cbrt] = lambda x: 1./(3.*np.cbrt(x)**2)
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class Uncertainty(object):

‎astropy/uncertainty/tests/__init__.py

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‎astropy/uncertainty/tests/test_uquantity.py

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# coding: utf-8
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# Licensed under a 3-clause BSD style license - see LICENSE.rst
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"""
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Test the Quantity class and related.
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"""
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from __future__ import (absolute_import, unicode_literals, division,
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print_function)
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import numpy as np
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from ...tests.helper import pytest
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from ... import units as u
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from ... import constants as c
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from .. import UQuantity
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def test_initialisation():
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v1 = UQuantity(5, 2, u.km)
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assert v1.value == 5
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assert v1.unit == u.km
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assert v1.uncertainty == 2
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v2 = UQuantity(5 * u.km, 2)
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assert v2.value == 5
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assert v2.unit == u.km
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assert v2.uncertainty == 2
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v3 = UQuantity(5 * u.km, 2000 * u.m)
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assert v3.value == 5
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assert v3.unit == u.km
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assert v3.uncertainty == 2
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v4 = UQuantity(np.arange(5.), 2., u.km)
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assert np.all(v4.value == np.arange(5.))
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assert v4.unit == u.km
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assert v4.uncertainty == 2
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v5 = UQuantity(np.arange(5.), np.array([1., 2., 1., 2., 1.]), u.km)
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assert np.all(v5.value == np.arange(5.))
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assert v5.unit == u.km
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assert np.all(v5.uncertainty == np.array([1., 2., 1., 2., 1.]))
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class TestBasics():
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def setup(self):
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self.v = UQuantity(5., 2., u.km)
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self.a = UQuantity(np.arange(1., 5.), 1., u.s)
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self.b = UQuantity(np.array([1., 2., 3.]), np.array([0.1, 0.2, 0.1]),
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u.m)
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def test_addition(self):
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c1 = self.v + UQuantity(12, 5, self.v.unit)
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assert c1.value == self.v.value + 12
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assert c1.unit == u.km
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# Uncertainties under addition add in quadrature
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assert np.allclose(c1.uncertainty,
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np.sqrt(self.v.uncertainty**2 + 5**2))
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# now with different units
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c2 = self.v + UQuantity(12000., 5000., u.m)
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assert c2.value == self.v.value + 12
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assert c2.unit == u.km
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assert np.allclose(c2.uncertainty,
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np.sqrt(self.v.uncertainty**2 + 5**2))
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# try array
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c3 = self.v + self.b
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assert np.all(c3.nominal_value ==
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self.v.nominal_value + self.b.nominal_value)
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assert np.allclose(c3.uncertainty,
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np.sqrt((self.v.uncertainty * self.v.unit)**2 +
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(self.b.uncertainty * self.b.unit)**2)
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.to(c3.unit).value)
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# try adding regular Quantity
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c4 = self.v + 10. * self.v.unit
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assert c4.value == self.v.value + 10.
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assert c4.uncertainty == self.v.uncertainty
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def test_subtraction(self):
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c1 = self.v - UQuantity(12, 5, self.v.unit)
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assert c1.value == self.v.value - 12
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assert c1.unit == u.km
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# Uncertainties under addition add in quadrature
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assert np.allclose(c1.uncertainty,
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np.sqrt(self.v.uncertainty**2 + 5**2))
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def test_multiplication(self):
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c1 = self.v * self.a
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assert np.all(c1.nominal_value ==
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self.v.nominal_value * self.a.nominal_value)
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# Fractional uncertainties under multiplication add in quadrature
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assert np.allclose(c1.uncertainty/c1.value,
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np.sqrt((self.v.uncertainty/self.v.value)**2 +
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(self.a.uncertainty/self.a.value)**2))
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# Test multiplication with straight Quantity
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c2 = self.a * (10. * u.s)
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assert np.all(c2.value == self.a.value * 10.)
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assert c2.unit == self.a.unit * u.s
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assert np.all(c2.uncertainty == self.a.uncertainty * 10.)
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def test_division(self):
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c1 = self.v / self.a
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assert np.allclose(c1.value, (self.v.nominal_value /
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self.a.nominal_value).to(c1.unit).value)
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# Fractional uncertainties under division add in quadrature
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assert np.allclose(c1.uncertainty/c1.value,
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np.sqrt((self.v.uncertainty/self.v.value)**2 +
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(self.a.uncertainty/self.a.value)**2))
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def test_more_complex():
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G = UQuantity(c.G, subok=False)
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m1 = UQuantity(1e15, 1e5, u.kg)
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m2 = UQuantity(100, 10, u.kg)
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r = UQuantity(10000, 500, u.m)
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F = G * (m1 * m2) / r**2
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assert np.allclose(F.value, 6.67384e-11 * (1e15 * 100) / 10000**2)
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assert F.unit == u.N
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# Uncertainties calculated using partial derivative method
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assert np.allclose(F.uncertainty, np.sqrt(
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(m1.value*m2.value/(r.value**2)*G.uncertainty)**2 +
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(G.value*m2.value/(r.value**2)*m1.uncertainty)**2 +
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(G.value*m1.value/(r.value**2)*m2.uncertainty)**2 +
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(-2*G.value*m1.value*m2.value/(r.value**3)*r.uncertainty)**2))

‎astropy/uncertainty/uquantity.py

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# -*- coding: utf-8 -*-
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# Licensed under a 3-clause BSD style license - see LICENSE.rst
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from __future__ import (absolute_import, division, print_function,
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unicode_literals)
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import numpy as np
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from ..units import Quantity
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from .core import Variable
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__all__ = ["UQuantity"]
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class UQuantity(Variable, Quantity):
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def __new__(cls, value, uncertainty=None, unit=None, **kwargs):
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if uncertainty is None:
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uncertainty = getattr(value, 'uncertainty', None)
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value = getattr(value, 'nominal_value', value)
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subok = kwargs.pop('subok', True)
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if subok and isinstance(value, Quantity):
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q_cls = type(value)
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cls = _subclasses[q_cls]
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else:
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q_cls = Quantity
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value = q_cls(value, unit, **kwargs)
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if uncertainty is not None:
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uncertainty = q_cls(uncertainty, value.unit)
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return super(UQuantity, cls).__new__(cls, value, uncertainty, **kwargs)
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@property
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def uncertainty(self):
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return (0 if self._uncertainty is None
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else self._uncertainty().to(self.unit).value)
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def __quantity_subclass__(self, unit):
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q_cls = self._nominal_value.__quantity_subclass__(unit)[0]
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return _subclasses[q_cls], True
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def __str__(self):
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return '{0}±{1}{2:s}'.format(self.value, self.uncertainty,
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self._unitstr)
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def __repr__(self):
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prefix1 = '<' + self.__class__.__name__ + ' '
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if self.isscalar:
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return '{0}{1}±{2}{3:s}>'.format(prefix1, self.value,
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self.uncertainty, self._unitstr)
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prefix2 = ' ' * (len(prefix1) - 1) + '±'
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valstr = np.array2string(self.value, separator=',', prefix=prefix1)
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errstr = np.array2string(self.uncertainty, separator=',',
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prefix=prefix2)
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return '{0}{1}\n{2}{3}{4:s}>'.format(prefix1, valstr,
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prefix2, errstr, self._unitstr)
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class _SubclassDict(dict):
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def __getitem__(self, q_cls):
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if q_cls not in self:
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# Use str('U') to avoid unicode for class name in python2.
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self[q_cls] = type(str('U') + q_cls.__name__,
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(UQuantity, Variable, q_cls), {})
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return super(_SubclassDict, self).__getitem__(q_cls)
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_subclasses = _SubclassDict()
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_subclasses[Quantity] = UQuantity

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